In a vertical semiconductor device which includes electrodes on a front surface and a rear surface of a semiconductor layer, a termination structure such as a RESURF or a guard ring is provided in the periphery of an element region in order to increase a breakdown voltage. By providing the termination structure, electric field concentration at an end portion of the element region is reduced, and avalanche breakdown is prevented from occurring at the end portion of the element region.
It is preferable that a vertical semiconductor device in which avalanche breakdown does not occur at the end portion of the element region be designed such that the avalanche resistance of the vertical semiconductor device increases. The reason for this is that, if the avalanche breakdown occurs at the end portion of the element region, element breakdown easily occurs, compared to the case in which avalanche breakdown occurs inside the element region.